1. Field of the Invention
This invention relates to a novel functional polypeptide, and, in particular, to a novel functional polypeptide which contains the cell-binding domain peptide of human fibronectin and the heparin-binding domain peptide of human fibronectin, to a method for its preparation; and also to the use of such functional polypeptide to inhibit angiogenesis.
2. Prior Art
Fibronectin (hereinafter referred to as FN) is a glycoprotein found in the plasma and extracellular matrix and has a number of functions (Annu. Rev. Biochem., 57, 375-413, 1988). Natural FN has been tested for use in pharmaceutical products such as in the treatment of wounds and in eye drops and also for use in cosmetics, but because natural FN is obtained from blood, its supply is limited, and its cost is high. In addition, because it may be contaminated with pathogenic bacteria and viruses, it is not in practical use at the present. For the same reasons, the functional domain of FN has not been isolated for use in practical applications.
Angiogenesis, which is the growth of new blood vessels, including capillaries, is known to be related to the progress of the disease in disorders such as chronic inflammations, certain immune reactions, and carcinogenesis. For that reason, a substance which inhibits angiogenesis may be able to largely inhibit the growth of tumors, the progress of retinopathy and chronic articular rheumatism, the spreading of foci of psoriasis, and the like.
Up to the present, steroids including prednisolone, 6.alpha.-methylprednisolone, and dexamethasone have been found to inhibit angiogenesis induced experimentally in chick embryo chorions, rabbit corneas, and hamster cheek pouches.
In FN there are two regions which bind with heparin (hereinafter referred to as heparin-binding domains), one of which is near the N-terminal and Ca ions are needed for binding at this domain. The other region is near the C-terminal, and the activity in the binding of this region to heparin is greater than the binding activity of the N-terminal region, with Ca ions having no effect on binding.
Recent research has shown that the heparin-binding domain of FN is important in the attachment, spreading, and movement of fibroblasts, endothelial cells, and certain kinds of tumor cells, just as the cell-binding domain is important. The heparin-binding domain of FN binds with the proteoglycans on the surface of the cells, and gives rise to interactions between the cell and extracellular matrix, thus contributing to cell attachment, spreading, and movement. Therefore, a polypeptide with both of the functions of cell-binding activity and heparin-binding activity can be expected to be of use in pharmaceutical preparations and the like by contributing to the healing of wounds by binding in the region of the wound with both cells and the extracellular matrix, and also by helping to maintain the normal condition.
The object of this invention is to provide a novel functional polypeptide which has both the functions of the cell-binding activity of FN and the heparin-binding activity of FN, to provide a method for the preparation of such a functional polypeptide, and to provide a novel agent for the inhibition of angiogenesis which makes use of a substance which is related to substances in the body and which is safe.